Younger Brother's Folly
The Unformed are probably Younger Brother's strangest creation. Creatures of limitless possibility, the Unformed can take any shape they please, with one restriction. Once they leave a specific form, they can never again return to it. This has massive cultural and spiritual significance to the Unformed, as they consider the changing of form to be akin to the death of the original being and its replacement with a new, similar one. This is functionally true, as inhabiting a new form essentially changes everything about an Unformed.
The Unformed live in nomadic tribes that wander across Leshii. Their mystical connection to the land allows them to move safely across the evershifting surface of the planet. Many believe this connection is why the Unformed took the events of The Reaving even worse than the other races.